1. Field of the Invention
The invention relates to reverse osmosis (RO) residential/commercial drinking water systems, and more specifically to an apparatus and method for reducing the generation of waste water outlet in an RO system.
2. Description of Related Art
Osmosis is a naturally occurring phenomenon and one of the most important processes in nature. It is a process where a weaker saline solution will tend to migrate to a strong saline solution; that is, a solution that is less concentrated will have a natural tendency to migrate to a solution with a higher concentration. Reverse osmosis occurs when the solution is moved across a membrane against the concentration gradient, from lower concentration to higher concentration. For example, under normal osmosis, a semipermeable membrane with fresh water on one side and a concentrated aqueous solution on the other side would have the fresh water cross the membrane to dilute the concentrated solution. In reverse osmosis, pressure is exerted on the side with the concentrated solution to force the water molecules across the membrane to the lower concentration side.
Reverse osmosis is utilized as a water purification technology employing a semipermeable membrane to remove larger particles from drinking water. A semipermeable membrane is a membrane that will allow some atoms or molecules to pass but not others. Reverse osmosis can remove many types of molecules and ions from solutions, including bacteria, and is used in both industrial processes and the production of potable water. The predominant removal mechanism in membrane filtration is straining, or size exclusion.
The desalinated water that is demineralized or deionized is typically called permeate (or product) water. In a one stage RO system, the feed water enters the RO system as one stream and exits the RO as concentrate and permeate water. The water stream that carries the concentrated contaminants that did not pass through the RO membrane is called the waste (reject or brine) stream.
Generally, in an RO system, water containing impurities enters the system where the impurities are stopped and rejected at the membrane surface. Water pressure then forces water molecules through the membrane. The purified water is then sent directly to the faucet. Impurities are then expelled from the system and sent to a drain underneath the sink area.
As a consequence of an RO system, a portion of the water supply must be used to flush the contaminants to drain. Thus, there is a usage (waste) factor that can represent a significant portion of the total water use.
In U.S. Pat. No. 8,083,936 issued to Walker on Dec. 27, 2011 titled “REDUCING WASTE WATER IN REVERSE OSMOSIS RESIDENTIAL DRINKING WATER SYSTEMS,” an RO system is taught where the production of product water is controlled by differential pressure across the purification membrane. As the tank pressure increases, the differential pressure decreases, and a reduced production of product water results. The increasing tank pressure is utilized as a force to actuate a valve that proportions the waste water (a proportioning valve) generally in a relationship to the product water. In this manner, the ratio between the product water and the waste water remains constant during the period that the purified water is being delivered to the holding tank.
FIG. 1 depicts a proportioning valve of the prior art. In this technology, proportioning valve 10 is inserted within an RO system. In the RO system, as pressure is increased in the system's storage tank, pressure tank water enters inlet 12. A piston 14 in the proportioning valve is forced through an O-ring 15 located within a piston housing 16, relocating the piston's position relative (and proportional to) a channel 18 in the piston, which is V-shaped, along and inside the surface portion of the piston. This V-shaped channel 18 slowly decreases in depth as it moves towards seal 13 on the piston. The channel being widest and deepest at the end proximate the ingress port 22. This allows the system to shut off when the tank pressure reaches approximately two-thirds of the line pressure, designed because of diminishing returns of product water in relation to waste water. A return spring 19 resides at the passage or channel end of the piston in a housing 20. Reject water enters the proportioning valve through ingress port 22 in piston housing 16. Reject water exits the proportioning valve through egress port 24 of housing 20 depending upon the positioning of piston 14. Waste water passes through V-shaped channel 18 and the passage surrounded by O-ring 15, and is discharged through egress port 24.
One of the deficiencies with the prior art design is that water enters the spring chamber where it can rust and degrade the life of the spring. Another deficiency is the inability to adjust the proportioning valve to accommodate the particular RO system in which it operates. A third deficiency is the application of numerous mechanical components that tend to degrade and/or fail over time.